The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
In conventional manual transmissions, it is possible, during very rapid clutch engagement, for the rate of torque increase across and through driveline components to equal or exceed their rated strengths. This can result in increased warranty issues and, ultimately, reduced service life of the components.
A peak torque limiting valve with a fixed orifice installed in the hydraulic fluid line between the clutch master and slave cylinders can be used to limit the flow rate of hydraulic fluid out of the slave cylinder and thus the engagement rate of the clutch such that the rate of increase of torque through the driveline components is also limited.
This approach to controlling maximum rate of torque increase in the vehicle driveline provides a viable solution in most instances. However, under low temperature conditions, the clutch hydraulic fluid will be more viscous and with lower and lower temperatures, the flow rate through the fixed orifice reduces correspondingly. This reduced flow rate under cold temperature conditions results in reduced clutch engagement rate as well as providing a clutch pedal feel which is anomalous and generally does not meet the customer's expectations. In extreme situations, when the clutch is released, the pedal may not return (rise) at the rate the driver raises his or her foot. The present invention addresses all of these issues.